Well tool for releasing liner hangers and the like



Jan. 30, 1968 J. R. SOLUM WELL TOOL FOR RELEASING LINER HANGERS AND THE LIKE 2 Sheets-Sheet 1 Filed Feb. 25,, 1965 Jan. 30, 1968 J. R. SOLUM 3,366,182

WELL TOOL FOR RELEASING LINER HANGERS AND THE LIKE Filed Feb. 25, 1965 i 2 h ets-Sheet 2 IN V'ENTER 12/1455 16 5040/14 United States Patent 3,366,182 WELL TOOL FOR RELEASING LINER HANGERS AND THE LIKE James R. Solum, Los Angeles, Calif., assignor to B & W Incorporated, Torrance, Califi, a corporation of California Filed Feb. 25, 1965, Ser. No. 435,199 11 Claims. (Cl. 166208) This invention relates to a tool for releasing liner hangers depending therefrom and in particular is directed to a'tool of this type which reliably and readily operates in the extreme conditions encountered in a well environment.

The tool of this invention constitutes an improved embodiment of that which is disclosed in United States Letters Patent No. 3,136,367, Liner Releasing Tool. This type of tool functions as a selectively operable disconnect device whereby a liner hanger and/or a liner depending therefrom may be released and left in the well at the desired location by operation of the tool through a simple manipulation of the well pipe from which the tool depends. For example, in the drilling and completion of oil wells a well casing or liner is cemented in place by lowering the casing or liner into the well bore by a drill pipe string with a releasing tool coupling the drill pipe to the well casing or liner whereby the drill pipe string may be removed upon completion of the cementing operation and the well casing or liner remains in the well bore. The tool of this invention and the tool of the aforementioned patent have the added advantage of permitting rotation of the well casing or liner without release thereof until the drill pipe string is manipulated to cause the releasing function.

As is well known to those skilled in the art, the environment encountered in a well bore includes extreme and objectionable conditions of pressure, temperature and fluid properties. The drilling fluid or mud in a well bore usually contains suspended solids and is unsatisfactory as a lubricant. Thus down-hole oil well tools which include relatively moving components are designed to avoid fouling by the drilling mud, such as by providing complete fluid sealing between the components to exclude the drilling mud. While such a fluid sealing arrangement accomplishes the function of excluding the drilling mud, a substantial pressure differential will develop as the tool is lowered in the well bore by reason of the presence of atmospheric pressure in the sealed passageways and chambers versus the fluid pressure in the well bore. This extreme pressure differential condition which is particularly aggravated in deep oil wells produces extreme frictional binding forces on normally moving components thereby rendering such components immovable. This characteristic or result is commonly referred to as hydraulic lock and renders the tool completely ineffective if such movement is necessary to its operation. Such an occurrence in a liner releasing tool used in a cementing operation is extremely objectionable in that the drill pipe thereby remains connected to the cemented liner and must be separated by breaking or cutting.

Another deficiency of liner releasing tools which has been observed to occur under certain conditions is the premature releasing of the liner before reaching the desired location in the well bore. In operating liner releasing tools of the type described in the aforementioned patent to cause the release of the liner, the drill pipe is set down on the releasing tool which is in turn supported by 3,366,182 Patented Jan. 30, 1968 the liner or a liner hanger and is rotated to effect the release. Occasionally, a liner or well casing is of such a light weight that the frictional resistance developed by centralizing devices and the like placed on the liner or well casing are suflicient to support the liner or well casing within the well bore. Under such circumstances, the drill pipe string must be set down on the releasing tool to force the liner or well casing down the well bore. Thus a liner releasing tool of this type will be continually in a position for causing release and the intermittent movement and rotation accompanying the lowering of a drill pipe string in a well bore can result in producing the re quired rotation of the tool to cause premature releasing Accordingly, it is a principal object of this invention'to provide a novel embodiment of a liner releasing tool which is not adversely affected by the conditions encountered and imposed throughout the lowering of the liner into a well bore.

An object of this invention is to provide a novel form or" well tool having selectively movable components and internal chambers wherein an incompressible fluid occupies such chambers to exclude contaminated well fluid and means assure no more than a minimal pressure difference between such fluids thereby permitting the operative movement of such tool components.

Another object of this invention is to provide a vertically collapsing tool with means for maintaining the extended conditions of the tool until collapsing is desired. A further object is to provide such means in a manner whereby the tool is returned to the extended position in the event that the tool is inadvertently moved toward the collapsed condition.

Still another object of this invention is to provide a novel form of well tool wherein internal chambers formed by cooperating components which move to change the volume of such chambers are filled with incompressible fluid and frangible means permit communication between the surrounding environment and such chambers upon excessive pressure ditferential therebetween. In particular, it is an object of this invention to provide a liner setting and releasing tool wherein an internal member is threaded for connection to the liner and is movable within such a fluid filled chamber thereby permitting movement of such internal member unaffected by surrounding fluid pressures.

Other and more detailed objects and advantages of this invention will appear from the following description and the accompanying drawings, wherein:

FIGURE 1 is an elevation view of the tool of this invention with a liner hanger and liner depending therefrom and positioned in a well casing in a well.

FIGURE 2 is an enlarged sectional elevation of the tool of this invention with the components in their respective positions prior to releasing.

FIGURE 3 is a sectional elevation similar to FIGURE 2 with the components in their respective positions illustrating a partially released condition of the tool.

FIGURE 4 is a fragmentary sectional elevation of modified form of a portion of the tool shown in FIG- URES l, 2 and 3.

FIGURE 5 is a fragmentary sectional plan view taken substantially on the line 55 of FIGURE 2 and illustrating the means for permitting fluid communication between the interior and the exterior of the tool on reaching predetermined pressure differential levels.

FIGURE 6 is an exploded perspective view of the removable means shown in FIGURE for permitting such fluid communication.

FIGURE 7 is a fragmentary and somewhat diagrammatic sectional elevation of that portion of the tool which contains the means for permitting such fluid communication and with the tool oriented horizontally for filling the internal chambers with incompressible fluid prior to lowering the tool into the well.

FIGURE 8 is an enlarged fragmentary sectional elevation taken substantially on line 8-8 of FIGURE 4 and showing a portion of such modified embodiment in detail.

Referring in detail to FIGURE 1, the well pipe or liner 10 that is to be lowered into the well casing 11 is connected by a coupling 12 to the lower end 13 of a liner hanger, generally designated 14. Liner hanger 14 may be of any convenient type and forms no part of this invention. The illustrated liner hanger 14 is of the type described in United States Letters Patent No. 3,012,612 wherein the casing engaging slips 15 are actuated by a collar member 16 which is in turn actuated by a slidably mounted centralizer 17 adapted to be actuated upon the accomplishment of predetermined vertical movements. With the slips 15 engaging the casing, the liner 10 depends from the liner hanger 14 and therefore is supported at the proper location within the well casing 11. If it is desired to position a particular well pipe or liner on the bottom of the well bore, then the liner need not be hung within the well casing and therefore the liner hanger 14 may be eliminated. When the liner hanger 14 is eliminated, the tool of this invention is connected directly to the top of the liner, such as at the coupling 12, and the tool functions the same in all other respects. Often, it is conventional to mount centralizers 18 and other devices such as scratchers on the exterior of the liner 10 and aside from their normal functions these devices frictionally engage the casing 11 thereby producing frictional forces resisting the lowering of the liner into the well. It often occurs that the liner 10 is relatively light and such frictional forces are relatively high whereby it is necessary to push the liner down the well by resting the weight of the well pipe positioned thereabove on top of the liner. The significance of this condition will be pointed out in connection with the hereinafter presented description of the well tool of this invention.

The liner releasing tool of this invention, generally designated 20, is similar in overall construction and operation to the tool disclosed and described in United States Letters Patent No. 3,136,367, Liner Releasing Tool. The tool 20 is rovided with a tubular mandrel 21 upon which is mounted a collar member 22 and a bushing 23. A sleeve 24 is threadedly connected to collar 22 and has an upwardly facing internal shoulder 25 for engaging a mating downwardly facing shoulder on the bushing 23 whereby the bushing 23 is supported and retained within sleeve 24. The upper end 26 of the liner hanger 14 (or the upper end of the liner itself if the hanger is eliminated as noted above) is provided with internal left hand threads 27 for mating with the external left hand threads 28 provided on the lower end of bushing 23. The upper extremity of end 26 is provided with notches 29 for mating with lugs 30 on the lower extremity of sleeve 24 to form a rotational drive means between the sleeve 24 and end 26.

The mandrel 21 is provided with longitudinally extending and circumferentially spaced lugs 31 for selectively mating with slots 32 in collar 22 or slots 33 in bushing 23 to form splinetype drives. With lugs 31 engaging the slots 32 of collar 22, rotation of mandrel 21 serves to cause rotation of sleeve 24, end 26, liner hanger 14 and liner 10 which is usually desirable immediately prior to cementing the liner in place. By lowering mandrel 21 to position lugs 31 in the slots 33 of bushing 23, right hand rotation of mandrel 21 will cause unthreading of bushing 23 from top 26 as is shown in progress in FIGURE 3. When the mandrel 21 is lowered to this position, a thrust flange 34 engages the upper end 35 of collar 22. Thrust flange 34 is rotatably mounted on mandrel 21 and cooperates with a coupling member 36 to capture balls 37 therebetween and form a thrust bearing for rotatably supporting the mandrel 21, coupling 36 and components thereabove on the collar 22 and ultimately on the liner hanger. In this manner the threaded bushing 23 is connected to the mandrel 21 by a floating spline arrangement and therefore the mandrel does not impose resistive axial forces on the bushing during rotation. Various seals 38 are provided on collar 22 and bushing 23 for accomplishing sealing engagement with mandrel 21, sleeve 24 and upper end 26 thereby excluding foreign materials and fluids which might otherwise prevent the required movements of mandrel 21 and bushing 23. As thus far described, the tool 20 is substantially similar to the aforementioned liner releasing tool of United States Letters Patent 3,136,367.

Means are provided for retaining the mandrel 21 in the upper or extended position shown in FIGURE 2 and these means may include a tubular housing 40 mounted on collar 22 and extending upwardly beyond coupling 36. A coil compression spring 41 encircles a tubular member 42 and extends between the upper end of housing 40 and a nut 43. Nut 43 is threadedly mounted on member 42 for adjusting the amount of pre-compression of spring 41 to accommodate the particular condition. A set screw 44 may be provided for locking nut 43 in the desired position. The upper end of tubular member 42 is then connected through a conventional coupling 45 to the conventional drill pipe string which is employed in lowering tools into the well bore. The lower end of tubular member 42 is threadedly connected to coupling 36 which is in turn connected to mandrel 21. Thus downward movement of mandrel 21 relative to collar 22 is resiliently resisted by compression spring 41. This serves to maintain the tool in an extended condition thereby preventing intermittent engagement of the lugs 31 of mandrel 21 with the upper end of bushing 23 as the tool and liner are lowered into the well. As previously described, some liners 10 must be pushed into the well and therefore without this tool-extending arrangement the lugs 31 would engage slots 33 of bushing 23 during each downward movement of the liner and tool. As is well known, the lowering of a well pipe string in a well includes upward movement for a short distance after the attachment of each additional joint of pipe at surface level in order to release the pipe gripping spider. With the liner releasing tool of United States Letters Patent No. 3,136,367, this upward and then downward movement of the drill pipe often resulted in intermittent disengagement and reengagement of lugs 31 with slots 33 of bushing 23 which in turn occasionally caused inadvertent unthreading of bushing 23 thereby prematurely releasing the liner. By appropriately adjusting the force exerted by spring 41, the force required to push a liner into the well may be transmitted from coupling 45 through nut 44, spring 41 and housing 40 to collar 22 rather than through coupling 36 and thrust flange 34 to collar 22, thereby eliminating the longitudinal collapsing of the tool during such movement of the liner. However, with the liner hanger 14 set in the well casing or the liner 10 supported at the bottom of the well bore, the weight of the well pipe above the tool will be suflicient to cause collapsing of spring 41 to allow the lugs 31 to enter .slots 33 in bushing 23 to perform the releasing function, as shown in FIGURE 3. The minimum spacing between housing 40 and nut 43 is suflicient to permit engagement between thrust flange 34 and end 35 of collar 22 in the collapsed condition of the tool.

Referring now to FIGURE 4, a modified form of means are shown for accomplishing the aforedescribed function performed by housing 40, compression spring 41, tubular member 42, and adjustable nut 43 while the balance of the tool 20 is identical. An extension housing is threadedly connected to the collar 22 and encloses the coupling member 36 and thrust flange 34. A tubular member 52 is connected between coupling member 36 and conventional coupling 45. A cylinder housing 53 is concentrically mounted on tubular mandrel 52. The upper portion 54 of extension housing 50 is closely spaced from tubular member 52 and supports an annular piston 55 connected to the upper end. A ring flange 56 is connected to cylinder housing 53 below piston 55 and both slidably and sealably engages the outer surface of upper portion 54. A floating piston 57 is mounted within cylinder housing 53 for separating a compressible fluid chamber 58 from the incompressible fluid 59 filling the cylinder housing 53 below piston 57. Piston 57 is free to move for accommodating volumetric changes within cylinder housing 53 which will occur upon relative movement of the various components. Referring specifically to FIGURE 8, piston 55 is provided with a check valve assembly mounted therein including a ball 60 biased by a spring 61 to seat the ball. This arrangement permits relatively unencumbered fluid flow downward through piston 55 upon achieving appropriate fluid pressure differentials but prevents upward fluid flow therethrough. A small orifice 62 is provided through piston 55 for permitting restricted though continuous fluid flow in either direction through piston 55. When there is an aflirmative dowward pull on tool as by a heavy liner, the components of the arrangement will be in the position shown in FIG- URE 4 with substantially all of the fluid 59 positioned above piston 55. When under the aforedescribed circumstances it is necessary to push a liner into the well, downward movement of tubular member 52 relative to housing 50 (and therefore downward movement of mandrel 21 relative to collar 22) will be resisted by the necessity of forcing fluid 59 through the check valve assembly and orifice 62 in piston 55. The check valve also functions asa pressure release valve to allow the passage of fluid only after sufficiently high fluid pressures are reached. As with the aforedescribed adjusting nut 43, the compression of spring 61 is adjusted by screws 63'to prevent opening I of this check valve under the forces that will be encountered during pushing of the liner downwardly in the well. However after the liner hanger 14 has been anchored in place, the extreme downward forces applied on tubular member 52 will cause opening of the ball 60 to allow the passage of fluid thereby allowing the mandrel 21 to move downwardly for interengagement between lugs 31 and slots 33. Sustained upward pulling on tubular member 52 will eventually cause all of the fluid to pass through orifice 62 thereby causing the device to return to the condition shown in FIGURE 4 and such a procedure might be necessary to remedy the inadvertent collapsing of the tool during lowering as might occur upon inadvertent setting of the liner hanger 14.

Again referring to FIGURES 2 and 3, a chamber 70 is formed within tool 20 and bounded by mandrel 21 on the inside, sleeve 24 on the outside, collar 22 above, and bushing 23 below. The chamber 70 provides space for the bushing 23 to move upwardly into during the unthreading movement illustrated in FIGURE 3. This space must be unobstructed in order to permit free upward movement of the bushing 23 during the releasing operation. As described above, the various seals 38 prevent the fluid from the surrounding environment from entering these internal positions of the tool including chamber 70. While these seals successfully exclude the enviornmental fluid with accompanying foreign materials to insure an obstructed chamber 70, normally this would cause extreme pressure differentials between the atmospheric pressure retained in chamber 70 and the well environment pressure as will be imposed on the various components. Thus an extreme pressure force will be applied to the lower end of bushing 23 in deep oil wells and this can cause the aforedescribed binding or hydraulic lock to prevent unthreading of bushing 23.

Means are provided for preventing such extreme pressure differentials by permitting restricted fluid communication between chamber 70 and the environment and, as shown in the drawings, these means may include rupturable port assemblies 71 in the wall of sleeve 24. Each rupturable port assembly includes a disc 72 surmounted by a hollow screw 74. As shown in FIGURE 5, a port 75 communicates chamber 70 with the central portion of the interior side of disc 72 and the hollow screw 74 and opening in washer 73 communicates the surrounding environment with the central portion of the exterior surface of disc 72. Disc 72 may be of any convenient material for permitting fluid flow through the wall of sleeve 24 upon the occurrence of a predetermined level of pressure differential between chamber 70 and the surrounding environment. For example, conventional aluminum foil of a thickness of approximately .002 inch to .003 inch has been found to be a satisfactory material with the hole of washer 73 approximately A; inch diameter, whereby the disc will rupture upon the occurrence of approximately 250 pounds per square inch pressure differential. While one or more rupture port assemblies 71 may be provided in communication with chamber 70, it is preferred that at least two such port assemblies be provided on the same side of sleeve 24 to facilitate the filling of chamber 70 with fluid as shown in FIGURE 7.

Preparatory to lowering the apparatus shown in FIG- URE 1 into the well, the tool 20 is connected to the liner hanger 14 by tightly threading the bushing 23 into the threads 27, which is accomplished by left hand rotation of mandrel 21 with lugs 31 engaging slots 33. With the screw 74, washer 73 and disc 72 removed from the two ports on the same side of sleeve 24 and with the tool positioned horizontally as shown in FIGURE 7, a source of relatively incompressible fluid such as oil is connected to one of the ports by a hose 76. The fluid is forced into the chamber 70 until the chamber is full and such fluid overflows through the other port 77. The hose 76 is removed and the two rupture port assemblies 71 each comprising a disc 72, washer 73 and screw 74 are installed. Excess fluid in the port is removed to prevent rupturing of discs 72 while installing the port assembly 71. In this manner the chamber 70 is occupied by a clean incompressible fluid which forms no obstruction to movement of bushing 23 into the chamber. The pressure differential between chamber 70 and the surrounding environment cannot exceed the low level rupture strength of disc 72 thereby avoiding the binding forces or hydraulic lock otherwise occurring in tools of this type having sealed internal chambers. When disc 72 ruptures to equalize the internal and external pressures, the intrusion of fluid from the surrounding environment will be minimal due to the small size of ports 75 and the clean incompressible fluid filling chamber 70. Even if a disc 72 has not ruptured prior to unthreading of bushing 23, the movement of bushing 23 will not be impaired seriously since a disc 72 will rupture to permit the outflow of fluid as bushing 23 moves into chamber 70.

Having fully described my invention it is to be understood that I do not wish to be limited to the details herein set forth or to the details illustrated in the drawings, but my invention is of the full scope of the appended claims.

I claim:

1. An oil well tool adapted for selective operation in an oil well environment at a substantial downhole depth, comprising a body having a chamber enclosed from thewell environment, an element positioned in said body and movable relative to said chamber to change the volume of said chamber upon operation of the tool, means sealing. said chamber from the well environment, a relatively incompressible fluid substantially filling said chamber, and means normally closing said chamber for retaining said fluid in said chamber and said last-mentioned means operable for permitting restricted fluid communication in both directions between said chamber and the well environment only upon the occurrence of a predetermined pressure diflerential in either direction therebetween, said restricted fluid communication permitted by said last-mentioned means being less than a free flow and exchange of fluid between said chamber and the well environment.

2. The oil well tool of claim 1 wherein said means for normally closing said chamber and operable for permitting restricted field communication include a port extending between said chamber and the well environment, a rupturable disk positioned in said port, and means for replaceably mounting said disk in said port in a manner to expose the disk to pressure from both the chamber and the well environment, said disk being rupturable upon subjection to excessive pressure to open said port.

3. The well tool of claim 2, wherein the said port and means for mounting the disk combine to form an orifice of predetermined small size upon rupturing of said disk to permit restricted fluid communication and yet prevent free fluid circulation tending to allow intrusion of foreign material into said chamber.

4. An oil well tool adapted for selective operation in an oil well environment at a substantial downhole depth, comprising a body having a chamber enclosed from the well environment, an element positioned in said body and movable relative to said chamber to change the volume of said chamber upon operation of the tool, actuating means mounted for selective movement to a position for causing said movement of said element, means interconnecting said body and said actuating means for resisting inadvertent movement of said actuating means to said position, a relatively incompressible fluid substantially filling said chamber, and means normally closing said chamber for retaining said fluid in said chamber and said last-mentioned means operable for causing restricted fluid communication in both directions between said chamber and the well environment only upon the occurrence of a predetermined pressure differential therebetween.

5. The oil well tool of claim 4 wherein said means interconnecting said body and actuating means include a preloaded compression spring extending between said body and actuating means for resiliently urging said 'actuating means away from said position for causing movement of said element.

6. The oil well tool of claim 4 wherein said means interconnecting said body and actuating means include a fluid piston and cylinder assembly having means for allowing restricted fluid by-pass through said piston to permit movement of said actuating means to said position for causing movement of said element upon application of extreme downward force on said actuating means.

7. An oil well tool adapted for selective operation in an oil well environment at a substantial downhole depth, comprising a body having a chamber enclosed from the well environment, means sealing said chamber from the well environment, an element positioned in said body and movable relative to said chamber to change the volume of said chamber upon operation of the tool, a mandrel mounted in said body and selectively movable to a position for causing said movement of said element, a relatively incompressible fluid substantially filling said chamber, a passageway providing restricted fluid communication be tween said chamber and the well environment, and a closure element positioned in and normally closing said passageway but irreversibly opening said passageway upon the occurrence of a predetermined substantial pressure differential between the chamber and well environment in either direction, said restricted fluid communication permitted by said passageway being less than a free flow and exchange of fluid between said chamber and the well environment.

8. An oil well tool adapted for selective operation in an oil well environment at a substantial downhole depth, comprising a body having a chamber enclosed from the Well environment, an element positioned in said body and movable into said chamber to change the volume of said chamber upon operation of the tool, a relatively incompresslble fluid substantially filling said chamber, a port communicating said chamber with the well environment, and rupturable means mounted in said port for normally closing said chamber to retain said fluid in said chamber and rupturable for permitting fluid communication between said chamber and the well environment through said port upon the occurrence of a predetermined substantial pressure differential in either direction therebetween, the said fluid communication permitted by said port being less than a free flow and exchange of fluid between said chamber and the well environment.

9. An oil well tool adapted for selectively rotating and releasing a liner in an oil well environment at a substantial downhole depth, comprising a body having means for engaging the liner and transmitting rotation thereto, said body having a chamber enclosed from the well environment, a bushing mounted in said body and having thread means for connecting to the liner, said bushing movable into said chamber to change the volume of said chamber upon rotation of said bushing to release said thread means from the liner, a mandrel mounted in said body and longitudinally movable to a position for rotating said bushing, means sealing said bushing with said mandrel and body, a relatively incompressible fluid substantially filling said chamber, and means normally closing said chamber for retaining said fluid in said chamber and said last-mentioned means operable for permitting restricted fluid communication in both directions between said chamber and the well environment upon the occurrence of a predetermined substantial pressure differential therebetween.

10. An oil well tool adapted for selectively rotating and releasing a liner in an oil well environment at a substantial downhole depth, comprising a body having means for engaging the liner and transmitting rotation thereto, said body having a chamber enclosed from the well environment, a bushing mounted in said body and having thread means for connecting to the liner, said bushing movable into said chamber to change the volume of said chamber upon rotation of said bushing to release said thread means from the liner, a mandrel mounted in said body and having means for engaging said body and said bushing for causing rotation thereof upon rotation of said mandrel, said mandrel being longitudinally movable between positions for said means to selectively engage said body and said bushing, means interconnecting said body and said mandrel for retaining said mandrel in engagement with said body and out of engagement with said bushing until applying extreme longitudinal force on said mandrel to cause movement to said bushing-engaging position, means sealing said bushing with said mandrel and body, a relatively incompressible fluid substantially filling said chamber, and means normally closing said chamber for retaining said fluid in said chamber and said last-mentioned means operable for permitting restricted fluid communication in both directions between said chamber and the well environment upon the occurrence of a predetermined substantial pressure differential therebetween.

11. An oil well tool adapted for selectively rotating and releasing a liner in an oil well environment at a substantial downwhole depth, comprising a body having means for engaging the liner and transmitting rotation thereto said body having a chamber enclosed from the well environment, a bushing mounted in said body and having thread means for connecting to the liner, said bushing movable into said chamber to change the volume of said chamber upon rotation of said bushing to release said thread means from the liner, a mandrel mounted in said body and having means for engaging said body and said bushing for causing rotation thereof upon rotation of said mandrel, said mandrel longitudinally movable between positions for said means to selectively engage said body and said bushing, means interconnecting said body and said mandrel for retaining said mandrel in engagement with said body and out of engagement with said bushing until applying extreme longitudinal force on said mandrel to cause movement to said bushing-engaging position, a relatively incompressible fluid substantially filling said chamber, a port communicating said chamber with the Well environment, and rupturable means mounted in said port for permitting fluid communication between said chamber and the well environment through said port upon the occurrence of a predetermined substantial pressure differential therebetween to rupture said rupturable means.

10 References Cited UNITED STATES PATENTS ERNEST R. PURSE-R, Primary Examiner.

CHARLES E. OCONNELL, Examiner.

0 IAN A. CALVERT, Assistant Examiner. 

1. AN OIL WELL TOOL ADAPTED FOR SELECTIVE OPERATION IN AN OIL WELL ENVIRONMENT AT A SUBSTANTIAL DOWNHOLE DEPTH, COMPRISING A BODY HAVING A CHAMBER ENCLOSED FROM THE WELL ENVIRONMENT, AN ELEMENT POSITIONED IN SAID BODY AND MOVABLE RELATIVE TO SAID CHAMBER TO CHANGE THE VOLUME OF SAID CHAMBER UPON OPERATION OF THE TOOL, MEANS SEALING SAID CHAMBER FROM THE WELL ENVIRONMENT, A RELATIVELY INCOMPRESSIBLE FLUID SUBSTANTIALLY FILLING SAID CHAMBER, AND MEANS NORMALLY CLOSING SAID CHAMBER FOR RETAINING SAID FLUID IN SAID CHAMBER AND SAID LAST-MENTIONED MEANS OPERABLE FOR PERMITTING RESTRICTED FLUID COMMUNICATION IN BOTH DIRECTIONS BETWEEN SAID CHAMBER AND THE WELL ENVIRONMENT ONLY UPON THE OCCURRENCE OF A PREDETERMINED PRESSURE DIFFERENTIAL IN EITHER DIRECTION THEREBETWEEN, SAID RESTRICTED FLUID COMMUNICATION PERMITTED BY SAID LAST-MENTIONED MEANS BEING LESS THAN A FREE FLOW AND EXCHANGE OF FLUID BETWEEN SAID CHAMBER AND THE WELL ENVIRONMENT. 